Hammer retarder for automatic firearms



Jan. 18, 1949. c, G A D 2,45,158

HAMMER RETARDER FOR AUTOMATIC FIREARMS l iled Sept. 11, 1946.

20 l g 4 /5 W4 John E. Gn-rn'nd.

Patented Jan. 18, 1949 NITED STATES PATENT oFFics HAMIVIER RETARDER FOR AUTOMATIC FIREARMS (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to improvements in automatic firearms and is directed more particularly to improvements in firearms of the type commonly referred to as the U. S. carbine, Cal. .30, M1.

It is a principal object of the invention to provide a firearm of the automatic type, (especially of the carbine type,as stated) with a novel trigger group assembly which permits the same to be selectively placed in safe, semi-automatic firing, or full automatic firing conditions. As a special feature, the action within the trigger assembly issuch that operation of the hammer of the firearm, when in full automatic firing condition, is delayed until the bolt member is fully locked, thereby insuring safety of operation during full automatic fire.

That is to say, the construction of the invention is so arranged that the operator of the firearm may readily select which of the said three conditions he desires and, furthermore, when the carbine is in full-automatic position, a delaying action is imparted to the movement of the hammer so that the firing pin will not' be struck until suflicient time has elapsed to insure that the bolt is locked.

As will appear, the construction of the invention is also such that by altering certain conditions respecting particular parts about to be described, the rate of full-automatic fire of the arm may be decreased as desired. This feature, together with the ability to readily adjust the firearm to any of the conditions of safe, automatic or semi-automatic fire, obviously renders the firearm more flexible for military use and it is all accomplished without any appreciable increase in cost of manufacture or any difiiculty in repair or replacement of parts.

The specific nature of the invention as Well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which: i

Fig. 1 is a side elevational view, partly in section, of a receiver and trigger guard group of an automatic firearm embodying this invention. In this figure, the .elements are shown with the hammer cocked, the trigger unpulled, and the selector set for semi-automatic fire.

Fig.2 is a side elevational view, partly in section, of .the trigger. guard group taken from the opposite side from Fig. 1. In this figure, the trigger is shown in its pulled position, the hammer in its fired position, and the selector set for automatic fire.

Fig. 3 is an elevational view of the selector.

Fig. e is a top elevational view of the inertia member.

Since the novel features of this invention are only concerned with the trigger group assembly, the components of the bolt assembly, stock assembly, gas system, etc., have not been shown in the drawings. However, it will be understood that the combination of parts forming this invention is intended to cooperate with the conventional operating parts of well known types of automatic firearms which are now in common use.

In Fig. 1 there is shown a receiver 2 having a trigger guard housing 4 with trigger 6 pivoted thereto on a pin 8. The usual trigger spring, indicated by It, operates in the conventional manner biasing the rear end of the trigger downwardly. The top portion of trigger S is bifurcated as indicated at l2 and a sear I 5 lies within the bifurcated portion and is pivotally mounted at its center on pin 8. The mounting hole in the sear comprises an elongated slot l8 which permits limited longitudinal movement of the sear with respect to the trigger. A sear spring 2t cooperates between a suitable seat in the sear and in the trigger to bias the sear forwardly with respect to the trigger.

A hammer member, shown at 22, is pivoted to the trigger guard, as by a pin 23, and is urged forwardly by a hammer spring 24 assembled on a guide rod 25 in the usual way. The hammer member is provided with a slot or cut portion 25 in a side thereof. Immediately below slot 26 a forwardly facing cam surface 29 is provided on hammer 22 which is arranged to engage a cam surface of an inertia member 44 which will be later described.

The forward end l5 of the sear is arranged to engage in a sear notch ll provided in the end of the cammed portion of the hammer. Thus, the hammer may be retained in cocked position by the sear.

What may be called a selector member 32 takes the place of the ordinary so-called safety. This consists of a rod-like member which extends laterally through the housing at a point forwardly of the trigger and is adapted to control the pivotal movement of the trigger. That is to say, the rod or selector member 32 is movable in ahorizontal plane at right angles to the trigger 3 and other moving parts between three selective positions now to be explained.

The trigger has a forwardly and downwardly projecting portion 34 which cooperates with the selector to limit the pivotal movement of the tri ger about the pin- First, there is a safety position wherein anysubstantial movement .of' the trigger is prevented; secondly, there is a semiautomatic firing position wherein the trigger may; be pulled a limited extent; andthirdly, a full automatic position wherein the trigger may be pulled an additional distance beyond its limiting position for semi-automatic fire.

When the selector 32 is in its safety position, it is in such position relative to the forward downwardly depending arm portion 34 0f the trigger member so that the latter will engage the peripheral surface 36 of the rod 32 andzthereby: prevent the trigger from moving sufiiciently to trip the sear I 4 to thereby release the hammer.

The selector 32'is provided with a vertical out 40 therein so that when the rod'is moved laterally from the safe position; said portion- 34 of the trigger is permitted to move downwardlya certain amount as illustrated in Fig. 1. Thus, upon pulling or-rearward movement of the trigger, the firearm fires semi-automatically; This is accomplished by virtue of the fact that thesear member [4 is-therebypermitted to pivot sufficiently so-asto disengagethe 'cocked hammer and allow it to trip'forward'to-st-rike the firing pin.

The rear portion of the-trigger is provided with an upstanding projection *38 which underlies the rear end of the sear l4; When the'selector is moved laterally 'slightlyso as to be set for semi-automatic fire, the'trigger may be pulled sufiiciently that theprojection 38 raises the rear end of the sear and disengages' the'front end I5 from the sear notch H in the hammer; .1

thereby releasing the hammer to fire-the car= tridge. When the forward endof the sear dis engages'fromthe sear notch in the hammer 22 the sear moves forward'slightly underth'e bias of sear spring 28 and such-forward movement by the recoiling motion of '.the bolt (not shown);

the sear notch H in the hammer.will: again be engaged by the forwardjend; i5r-iof;the' sear. even though the trigger'remainsi inthe pulled po sition. When the trigger?issreleasedrby the op erator the sear is. movedrearwardly witlmrespect to the trigger due :tOIthGfOICBTOf'thB hame mer spring 24, which is. much greatersthan that of sear spring 20. Thusthe rear end of the sear again overlies triggerzprojection 38 so that.pull-. ing the trigger againrwill; trip; the:sear1in.the manner described.

It is to be understood" that the operationsfjust described with respect to. theisafety and semi? automatic positions of the firearms do. not devi- I ate from the. conventionalmechanism, forexample the trigger mechanism of the U. S. carbine Cal. .30 M1, exceptas will now be explained.

Theselector 32. is provided. Withanother vertical cut or slot M whichis deeper than, and angularly displaced from, thepreviously mentioned cut 40. This obviously permits the trigger tobe pulled still further rearwardly; upon further lateral movement, plus a' slight rotation; of the selector.

This sets the selector in" full automatic" firing position. The first shot is fired in the same mam ner as described for semi-automatic fire and the rear end of the sear slips off the trigger projection. However, the trigger now may be pulled an additional distance and this distance is sufficien-tithat lthertop surface of: the trigger rengages the-.rear endbf'ithe seer; andithrough. this engagement the front end l5 of the sear is pivoted downwardly to a position where the sear notch l'l in ,the hammer is no longer contacted during tliegmovementmf-the hammer from its fired to its cocked position. Thus in automatic fire the hammerziszentirely free of the sear so long as the tri ger remains pulled.

O'nwhatis" virtually the opposite side of the selector 32 there is a cam slot 50 as shown in Fig. 3, which is adapted to receive one end portion off a. longitudinally extending plunger 52 held in" spring-pressed relation between the selector member 32 and the conventional magazine lock member-54 The slot* 50 preferably hasthree recesses orseats; suclras 56, 58arrd= 605 withthe third reeessofifiset or disposed in the ans gular portion of the slot; as showm As" will"- be apparent; this slot-' is arranged* to cooperate witlrthe' structure of tlie oppositeside ofthe' pin in sucha way that the latter is resil-i'ently'positioned inthe' selective manner above described.

The" upper rear end or th e hbusing' (as shown) isprovided with a horizontalcut or slot 30 which not only performs its usual functionot'cooperab in'g witha mounting lug 31 of the-firearmreceiver 2 but also-accomplishes a" new purpose which will' presentlyi= appear:

Pivoted'to-arr upstanding portion= 43=ot the trigger member;- as by' pin" 42% iswhat I prefer to call a 'weig-ht of in-ertia-"memb'er Mi This includes a bod-y portion 46 which; according" to the preferredforn'rshown; is bifurcated so as to straddle the housing but it is to be-understood that*the shapewrfornrof this portion is not as ii n-portantas" the fact that" it" is provided with sufiicient mass so thatit will'-*delaymovementof the ha-mmer'wh'emthelatter-is in full automatic position as will"beexplaii'iecl: In" any event, the member also includes as rearwardly; extending arm portion" 6'1 having a can? surface 48* for: ward-lypf' its' pivot pointfiforengaging camsur face 29 of the hammer and its rear extremity is in-the=form of adog"TB'-'which *is "adapted tobe received in the ffont "endiof the slot or'recess 30' previouslymentiened. Arm portion fl of the inertia member lies-'in ith'e path of the slot portion -26--ofthe'-ham*mer and-'f-hence does' not add to theoverall width of the trigger mechanism;

The inertia" member" may be" pivotallyy biased iii-many ways b'utaccordingto the'prel'erredform shown; the usual I trigger spring has one' of its upperend' portions, such as M, extended to engage the arm= portion 4! of member 4M and thereby, of course, urge it'upwa'rdlyagalnst'the weight of the-bbdy-portidn-"i thus'tendingto move-- the cam surface 48 into= the path" of* the hammer camsurfa-ce'i 9f" It will benoticedinfigt'l that'wh'errthe-firearm is in the semi-automatic firing position, the'isaid dog T8 is' seatedih th e recess 3ll' even when the triggerds pulled suchithatth'e' dog-thereby prevents, any substantial movementof the weight member on"its-pivot; As'ia' result,'the-weight 44 is' preventedfrom afictingithe =operation "of" the hammer, although" thelatter'is,v of" course; held against movement since the trigger cannot move.

However, when thefirearnr'is in its full'automatic fired position, as shown in Fig. 2, the dog 70 is withdrawn from recess 30 and the hammer is engaged and retarded by the inertia member through cooperative engagement of the cam surfaces 29 and 43 respectively.

This is accomplished by manually engaging head part 12 of the selector and rotating the same so as to allow the forward end portion 34 of the trigger to drop into the largest cut 4| thereof and thereby permit the inertia member to swing sufficiently on its pivot pin so that on pulling of the trigger, the dog moves forwardly out of the slot permitting inertia member 44 to pivot forwardly under the bias of spring arm 14 which will dispose the cam surface 48 on the inertia member in the path of cam surface '29 on the hammer. The consequent result is that the hammer does not immediately follow the bolt forwardly but strikes the firing pin after a delay sufficient' to insure that the bolt is locked.

It will thus be seen that by selection of the mass of the inertia member, the rate of fire may be decreased as desired. In addition, by varying the angle of the cam surface 48 and/ or the tension of the spring arm 14, it is possible to further delay the action of the hammer to a considerable extent and thereby achieve still further reduction in rate of fire.

As will be appreciated, while the operator of the firearm may adjust the firearm to any one of three conditions, the inertia member functions only when the selector is in its full automatic position. In the safe or automatic positions, the trigger cannot be pulled sufficiently to move the cam surface 48 of the inertia member forwardly in front of cam surface 29 on the hammer. In these positions, the dog member 10 lies in the rear assembly slot 30 of the trigger housing member, and thus prevents pivotal movement of inertia member 44 under the bias of spring arm 14.

I claim:

1. In an automatic firearm having a spring pressed hammer movable between a cocked and a firing position, a sear engageable with said hammer to retain said hammer in the cocked position, trigger means for moving said sear to a nonengaging position relative to said hammer, an inertia member movably mounted on the firearm and disposed in the path of said hammer as said hammer moves to its fired position, and cam means on said hammer engageable with said inertia member to move it out of the path of said hammer whereby the firing movement of said hammer is delayed.

2. In an automatic firearm having a. spring pressed hammer movable between acocked and a firing position, a sear engageable with said hammer to retain said hammer in the cocked position, trigger means for moving said sear to a nonengaging position relative to said hammer, an inertia member movable by said trigger means into the path of said hammer as said hammer moves to its fired position, and cam means on said hammer engageable with said inertia member to move it out of the path of said hammer whereby the firing movement of said hammer is delayed.

3. In an automatic firearm having a sprin pressed hammer movable between a cocked and a firing position, a sear engageable with said hammer to retain said hammer in the cooked position, a trigger operatively connected to said sear for moving said sear to a non-engaging position relative to said hammer, an inertia member pivotally connected to said trigger and movable by pulling movement of said trigger into the path of said hammer as said hammer moves to its fired position, and cam means on said hammer enga eable with said inertia member to move it out of the path of said hammer whereby the firing movement of said hammer is delayed.

4. In an automatic firearm having a spring pressed hammer movable between a cocked and a firing position, a sear engageable with said hammer to retain said hammer in the cooked position, trigger means for moving said sear to a nonengaging position, a trigger movably mounted on the firearm, means for selectively limiting the pulling movement of said trigger to either a semiautomatic firing position or an automatic firing position, means connecting said trigger and said sear for moving said sear to a non-engaging position relative to said hammer in said automatic firing position of said trigger, an inertia member pivotally connected to said trigger and pivotable by movement of said trigger to its said automatic firing position into the path of said hammer as said hammer moves to its fired position, and cam means on said hammer engageable with said inertia member to move it out of the path of said hammer whereby the firing movement of said hammer is delayed.

5. The combination defined in claim 4 and including means for preventing pivotal movement of said inertia member into the path of said hammer as said trigger is pulled to its semiautomatic firing position.

JOI-IN C. GARAND.

No references cited. 

